Reconfigurable optical transceiver for use with multiple modulation techniques

This application claims the benefit of U.S. Provisional Patent App. No. 63/332,310, entitled “Format Agnostic Receiver for Direct and Coherent Detection,” filed on Apr. 19, 2022, the disclosure of which is expressly incorporated herein by reference in its entirety.

This disclosure relates generally to optical communications, and more particularly to optical transceivers.

During this time of growth of Internet technologies and usage, demand for high speed data transmission has increased rapidly. As an example, average internet traffic in 2021 was estimated to exceed 700 terabytes per second. Technologies to support such sustained usage levels will continue to proliferate. Optical transmission of data can support vast amounts of data per channel—often limited more by the rate at which electronics can encode a signal onto the optical channel rather than the bandwidth of the channel itself. Improvements to optical modulation performance will continue to drive adoption of such technologies.

There are a number of different modulation techniques currently in use for optical communications. Examples of such modulation techniques include: i) intensity modulation techniques such as intensity-modulation, direct detection (IMDD), dual polarization IMDD; and ii) coherent modulation techniques such as quadrature phase shift keying (QPSK) modulation, dual polarization QPSK (DP-QPSK) modulation, differential QPSK (DQPSK) modulation, dual polarization DQPSK, M-ary quadrature amplitude modulation (M-QAM), dual polarization M-QAM, etc. A typical optical transceiver is capable of generating and receiving only one type of optical modulation (or a small subset of the various currently available types of optical modulation). For example, a typical optical transceiver capable of generating and receiving IMDD-modulated optical signals is not capable of generating or receiving QPSK- or M-QAM-modulated optical signals. As another example, a typical optical transceiver capable of generating and receiving QPSK- or M-QAM-modulated optical signals is not capable of generating or receiving IMDD-modulated optical signals.

In an embodiment, an optical module for use with multiple optical modulation techniques comprises: a plurality of lasers, each of at least some of the lasers configured to be selectively turned on and turned off depending on a type of modulation to be used, each laser corresponding to a respective wavelength; an optical modulation system comprising a plurality of optical modulators; and a reconfigurable optical network that is configured to selectively direct light from the plurality of lasers to the optical modulation system differently depending on the type of modulation to be used. In another embodiment, a method of controlling a reconfigurable optical module for transmitting information via an optical medium includes: determining, at a controller, a type of modulation that is to be used to transmit the information via the optical medium, the type of modulation being determined from a plurality of different types of optical modulation techniques, including at least a first type and a second type; controlling, by the controller, a plurality of lasers of the reconfigurable optical module to one of i) turn on or ii) turn off at least some of lasers among the plurality of lasers depending on the type of modulation to be used, each laser corresponding to a respective wavelength; and controlling, by the controller, a reconfigurable optical network of the reconfigurable optical module to selectively direct light from the plurality of lasers to an optical modulation system of the reconfigurable optical module differently depending on the type of modulation to be used.

In yet another embodiment, an optical module for use with multiple optical modulation techniques comprises: optical-to-electrical conversion circuitry that includes a plurality of photodiodes coupled to a plurality of transimpedance amplifiers (TIAs), the plurality of photodiodes including multiple-input photodiodes, each multiple-input photodiode including a first side and a second side that is opposite the first side; an optical processor that is configured to optically process one or more optical signals corresponding to coherent modulation, the optical processor being coupled to the plurality of photodiodes, including multiple outputs of the optical processor coupled to the respective first sides of the multiple-input photodiodes; and an optical network that is configured to i) in a first configuration corresponding to a first modulation technique, direct optical signals corresponding to light received via an optical medium to the respective second sides of the multiple-input photodiodes so that the light bypasses the optical processor, and ii) in a second configuration corresponding to a second modulation technique, direct one or more optical signals corresponding to light received via the optical medium to one or more inputs of the optical processor.

In still another embodiment, a method is for operating a reconfigurable optical module that includes optical-to-electrical conversion circuitry that includes a plurality of photodiodes coupled to a plurality of TIAs. The plurality of photodiodes includes multiple-input photodiodes, each multiple-input photodiode having a first side and a second side that is opposite the first side. The optical module further comprises an optical processor that is configured to optically process one or more optical signals corresponding to coherent modulation, the optical processor being coupled to the plurality of photodiodes. Multiple outputs of the optical processor are coupled to the respective first sides of the multiple-input photodiodes. The method includes: determining, at a controller, a type of modulation for which the reconfigurable optical module is to process optical signals received via an optical medium, the type of modulation being determined from a plurality of different types of optical modulation techniques, including at least a first type and a second type; and controlling, by a controller, a reconfigurable optical network of the reconfigurable optical module to selectively i) in a first configuration corresponding to a first modulation technique, direct optical signals corresponding to light received via the optical medium to respective first sides of the multiple-input photodiodes so that the light bypasses the optical processor, and ii) in a second configuration corresponding to a second modulation technique, direct one or more optical signals corresponding to light received via the optical medium to one or more inputs of the optical processor.

As discussed above, typical optical transceivers are capable of generating and receiving optical signals according to only one type of optical modulation (or a small subset of the various currently available types of optical modulation). For example, a typical optical transceiver capable of generating and demodulating amplitude-modulated optical signals is not capable of generating or demodulating coherent-modulated optical signals. As another example, a typical optical transceiver capable of generating and receiving coherent-modulated optical signals is not capable of generating and receiving amplitude-modulated optical signals.

In embodiments described below, a reconfigurable optical transmitter is capable of generating optical signals that are modulated according to various optical modulation techniques. As an illustrative example, an optical transmitter is capable of generating amplitude-modulated optical signals, and can be reconfigured to generate coherent-modulated optical signals, according to some embodiments.

The reconfigurable optical transceiver utilizes an innovative optical network that is reconfigurable to i) provide light from a plurality of lasers to respective inputs of an optical modulation system in a first configuration for amplitude-modulation, and ii) provide light from a single laser to multiple inputs of the optical modulation system in a second configuration for coherent-modulation, according to some embodiments.

In other embodiments described below, a reconfigurable optical receiver is capable of demodulating optical signals that are modulated according to various optical modulation techniques. As an illustrative example, an optical receiver is capable of demodulating amplitude-modulated optical signals, and can be reconfigured to demodulate coherent-modulated optical signals, according to some embodiments.

The reconfigurable optical receiver utilizes an innovative optical-to-electrical conversion circuit that is capable of processing optical signals that are modulated according to various optical modulation techniques, according to some embodiments. For example, the optical-to-electrical conversion circuit is capable of processing amplitude-modulated signals as well as coherent-modulated signals, according to some embodiments. On the other hand, typical optical receivers use either a first optical-to-electrical conversion circuit configured for processing amplitude-modulated signals or a second optical-to-electrical conversion circuit configured for processing coherent-modulated signals, i.e., where the first optical-to-electrical conversion circuit is different than the second optical-to-electrical conversion circuit.

1 FIG. 100 100 104 104 is a simplified diagram of an example optical transmitterthat is reconfigurable to generate amplitude-modulated and coherent-modulated signals, according to an embodiment. The optical transmittercomprises a baseband processor and modulation signal generator(sometimes referred to herein as the “baseband processor” for brevity) that is configured to i) receive data (e.g., from a host processor (not shown)) that is to be transmitted via an optical communication medium (not shown), and ii) use the received data to generate modulation signals.

100 108 104 108 104 The optical transmitteralso comprises an optical modulecoupled to the baseband processor. The optical moduleis configured to use the modulation signals from the baseband processorto generate an optical transmit signal for transmission via the optical communication medium.

104 The baseband processorincludes a digital signal processor (DSP, not shown) that is configured to perform various processing actions such as one or more of i) forward error correction (FEC) encoding, ii) signal pre-compensation, etc. Additionally, the DSP is also configured to map data that is to be transmitted to transmission symbols (e.g., to intensity levels for intensity modulation, to constellation points for M-QAM, etc.). The DSP is further configured to generate digital modulation signals based on the transmissions symbols.

104 The baseband processoralso comprises analog front end (AFE) circuitry (not shown) that is configured to generate analog modulation signals based on the digital modulation signals output by the DSP. For example, the AFE includes one or more analog-to-digital converters (ADCs) that are configured to convert the digital modulation signals to analog modulation signals.

104 112 108 112 104 112 112 112 112 The baseband processoralso comprises a controllerthat is configured to generate control signals for reconfiguring the optical modulefor generating the optical transmit signal according to different modulation techniques. In other embodiments, the controlleris external to the baseband processor. The controllercomprises a processor coupled to a memory, and the processor is configured to execute machine-readable instructions in the memory that, when executed by the processor, cause the controllerto generate the control signals, according to an embodiment. Additionally or alternatively, the controllercomprises hardware circuitry (e.g., a hardware state machine) that additionally or alternatively causes the controllerto generate the control signals, in another embodiment.

108 120 124 124 128 108 132 128 The optical modulecomprises a plurality of lasersoptically coupled to a reconfigurable optical network. The reconfigurable optical networkis optically coupled to an optical modulation system. The optical modulealso comprises driver circuitrycoupled to the optical modulation system.

120 120 112 108 120 120 112 108 120 120 112 In an embodiment, each laser in the plurality of lasersis configured to generate light at a respective wavelength. Each of at least some of the plurality of lasersis configured to be turned on and off based on a respective control signal from the controller. For example, in a first configuration of the optical modulemultiple lasers(e.g., all of the lasers) are turned on by control signals from the controller; whereas in a second configuration of the optical moduleonly one of the lasersis turned on and the remaining lasersare turned off by control signals from the controller.

124 120 128 112 108 112 124 120 128 108 112 124 120 128 In an embodiment, the reconfigurable optical networkis configured to direct light from the plurality of lasersto the optical modulation systemdifferently depending on control signals from the controller. For example, in the first configuration of the optical modulecontrol signals from the controllercontrol the reconfigurable optical networkto direct light from respective lasersat respective wavelengths to respective optical inputs of the optical modulation system; whereas in the second configuration of the optical modulecontrol signals from the controllercontrol the reconfigurable optical networkto direct light from one of the lasersto multiple optical inputs of the optical modulation system.

112 112 128 108 112 128 108 112 128 128 In an embodiment, the controllerconfigures, using modulation control signals generated by the controller, the optical modulation systemdifferently depending on the type of modulation to be used. For example, in the first configuration of the optical module, modulation control signals from the controllerconfigure the optical modulation systemfor a first type of modulation; whereas in the second configuration of the optical module, modulation control signals from the controllerconfigure the optical modulation systemfor a second type of modulation. As an illustrative example, the modulation control signals i) select a first modulator operating point of optical modulators of the optical modulation systemfor the first type of modulation, and ii) select a second modulator operating point (different than the first modulator operating point) of the optical modulators for the second type of modulation.

104 128 128 124 132 104 The driver circuitry is configured to condition modulation signals received from the baseband processorto generate conditioned modulation signals, and to provide the conditioned modulation signals to the optical modulation system. The optical modulation systemthen modulates light received from the reconfigurable optical networkbased on the conditioned modulation signals. In some embodiments, the driver circuitryis included in the baseband processor, for example as part of the AFE circuitry discussed above.

104 120 104 124 120 128 104 128 104 128 In operation, when data is to be transmitted via multiple wavelengths using intensity modulation, the baseband processorgenerates control signals to turn on multiple lasers. Additionally, the baseband processorgenerates control signals to configure the reconfigurable optical networkto direct light from respective lasersat respective wavelengths to respective optical inputs of the optical modulation system. Additionally, the baseband processorgenerates modulator control signals to configure optical modulators of the optical modulation systemfor intensity modulation. For example, the baseband processorgenerates modulator control signals to select an operating point of the optical modulators of the optical modulation systemto be a first modulator operating point suitable for intensity modulation.

104 132 132 128 128 Additionally, the baseband processorgenerates, using received data (e.g., from a host computer), modulation signals that correspond to intensity modulation, and provides the modulation signals to the driver. The driverthen provides conditioned modulation signals to the optical modulation system, which causes the optical modulation systemto modulate data onto the multiple wavelengths using intensity modulation.

104 120 120 104 124 120 128 104 128 104 128 On the other hand, when data is to be transmitted via a single wavelength using coherent modulation, the baseband processorgenerates control signals to turn on one lasersand to turn off the other lasers. Additionally, the baseband processorgenerates control signals to configure the reconfigurable optical networkto direct light from the one laserto multiple optical inputs of the optical modulation system. Additionally, the baseband processorgenerates modulator control signals to configure optical modulators of the optical modulation systemfor coherent modulation. For example, the baseband processorgenerates modulator control signals to select the operating point of the optical modulators of the optical modulation systemto be a second modulator operating point (different than the first operating point) suitable for coherent modulation.

104 132 132 128 128 Additionally, the baseband processorgenerates, using received data (e.g., from a host computer), modulation signals corresponding to coherent modulation, and provides the modulation signals to the driver. The driverthen provides conditioned modulation signals to the optical modulation system, which causes the optical modulation systemto modulate data onto the one wavelength using coherent modulation.

2 FIG.A 1 FIG. 2 FIG.A 1 FIG. 1 FIG. 200 200 108 200 100 100 200 is a simplified block diagram of an example optical modulethat can be reconfigured to generate an optical transmit signal according to different modulation techniques, according to an embodiment. The optical moduleis used as the optical moduleof, andis described with reference tofor ease of explanation. In other embodiments, the optical moduleis used in another suitable transmitter different than the transmitterof. Similarly, the transmitteruses a suitable optical module different than the optical module, in some embodiments.

200 204 204 204 204 204 120 1 FIG. The optical moduleincludes a plurality of lasers. In an embodiment, the plurality of lasersare configured to generate light at respective different wavelengths. For example, in a communication system that uses fiber optic cables conforming to the ITU standard G.652, the lasersare configured to generate light at 1271 nanometer (nm) (sometimes referred to as λ1); 1291 nm (sometimes referred to as λ2); 1311 nm (sometimes referred to as λ3); and 1331 nm (sometimes referred to as λ4). In other embodiments, the lasersgenerate at other suitable wavelengths. The laserscorrespond to the lasers(), in an embodiment.

200 208 208 212 212 208 The optical modulealso includes an optical modulation system. The optical modulation systemcomprises a plurality of optical modulators. In an embodiment, the optical modulatorscomprise Mach-Zehnder (MZ) modulators. In other embodiments, the optical modulation systemcomprises suitable optical modulators other than MZ modulators.

212 132 212 1 FIG. Each modulatorhas i) an optical input to receive light and ii) two modulation signal inputs configured to receive modulation signals, e.g., from driver circuitry (not shown) such as the driver circuitry(). Each modulatoris configured to modulate light received via the optical input based on the modulation signals received via the modulation signal inputs to generate a modulated optical output signal.

212 200 112 212 200 212 212 212 In an embodiment, the modulatorsare configured differently depending on the type of modulation to be used. For example, in a first configuration of the optical module, modulation control signals (not shown), from the controllerfor example, configure the modulatorsfor a first type of modulation; whereas in a second configuration of the optical module, the modulation control signals configure the modulatorsfor a second type of modulation. As an illustrative example, the modulation control signals i) select a first modulator operating point of the modulatorsfor the first type of modulation, and ii) select a second modulator operating point (different than the first modulator operating point) of the modulatorsfor the second type of modulation.

212 1 212 2 220 212 3 212 4 220 220 220 220 220 Outputs of the modulator-and the modulator-are combined and provided to a first input of a polarization beam rotator combiner (PBRC). Similarly, outputs of the modulator-and the modulator-are combined and provided to a second input of the PBRC. The PBRCis configured to combine light received via the two inputs of the PBRCwhile rotating polarization of light corresponding to light received by a first input of the PBRCby 90 degrees with respect to polarization of light corresponding to light received by a second input of the PBRC.

204 208 232 232 204 208 112 200 232 204 208 200 232 204 204 2 204 208 1 FIG. The lasersare optically coupled to the optical modulation systemvia a reconfigurable optical network. The reconfigurable optical networkis configured to direct light from the plurality of lasersto the optical modulation systemdifferently depending on received control signals, such as from a controller such as the controller(). For example, in a first configuration of the optical modulelaser control signals from the controller control the reconfigurable optical networkto direct light from each of the lasersto respective optical inputs of the optical modulation system; whereas in a second configuration of the optical modulelaser control signals control the reconfigurable optical networkto direct light from one of the lasers(e.g., the laser-or another suitable one of the lasers) to multiple optical inputs of the optical modulation system.

232 236 240 244 232 204 208 204 204 2 204 208 236 240 244 236 240 244 236 240 244 236 240 244 236 240 244 The reconfigurable optical networkcomprises a plurality of variable optical couplers,,that are arranged to, depending on a configuration of the reconfigurable optical network, either i) direct light from each of the lasersto respective optical inputs of the optical modulation system, or ii) direct light from one of the lasers(e.g., the laser-or another suitable one of the lasers) to multiple optical inputs of the optical modulation system. Each variable optical couplers,,includes a first optical input, a second optical input, a first optical output, a second optical output, and a control input. Each variable optical coupler,,is configured to direct light from the first optical input to the first optical output, and to direct light from the second optical input to the second optical output. Additionally, each variable optical coupler,,is configured to selectively optically cross-couple light from the first optical input to the second optical output, and to selectively optically cross-couple light from the second optical input to the first optical output. For example, when a laser control signal is in a first state, the variable optical coupler,,does not optically cross-couple light from the first optical input to the second optical output, and does not optically cross-couple light from the second optical input to the first optical output. On the other hand, when the laser control signal is in a second state, the variable optical coupler,,optically cross-couples light from the first optical input to the second optical output, and optically cross-couples light from the second optical input to the first optical output.

204 2 236 204 3 236 204 1 240 236 240 204 4 244 236 244 240 212 1 240 212 2 244 212 3 244 212 4 An output of the laser-is coupled to the first input of the variable coupler, and an output of the laser-is coupled to the second input of the variable coupler. An output of the laser-is coupled to the first input of the variable coupler, and the first output of the variable coupleris coupled to the second input of the variable coupler. An output of the laser-is coupled to the second input of the variable coupler, and the second output of the variable coupleris coupled to the first input of the variable coupler. The first output of the variable coupleris coupled to the optical input of the MZ modulator-, and the second output of the variable coupleris coupled to the optical input of the MZ modulator-. The first output of the variable coupleris coupled to the optical input of the MZ modulator-, and the second output of the variable coupleris coupled to the optical input of the MZ modulator-.

204 236 240 244 236 240 244 232 204 1 212 1 232 204 2 212 2 232 204 3 212 3 232 204 4 212 4 In operation, when data is to be transmitted via multiple wavelengths using intensity modulation, the laser control signals are set to turn on all of the lasers. Additionally, the optical network control signals are set to configure the variable couplers,,so that the variable couplers,,do not provide cross-coupling between the respective first input to the respective second output, and between the respective second input to the respective first output. As a result, the reconfigurable optical networkdelivers light from the laser-to the optical input of the MZ modulator-; the reconfigurable optical networkdelivers light from the laser-to the optical input of the MZ modulator-; the reconfigurable optical networkdelivers light from the laser-to the optical input of the MZ modulator-; and the reconfigurable optical networkdelivers light from the laser-to the optical input of the MZ modulator-.

212 212 Additionally, modulator control signals (not shown) configure the MZ modulatorsfor intensity modulation. For example, the modulator control signals select the operating point of the MZ modulatorsto be a first modulator operating point suitable for intensity modulation.

212 212 212 1 212 2 220 212 3 212 4 220 220 212 1 212 2 212 3 212 4 Additionally, the modulation signals control the MZ modulatorsto modulate respective data onto the respective light received by the MZ modulators. Further, modulated light from the MZ modulator-and modulated light from the MZ modulator-are combined and provided to the first input of the PBRC; and modulated light from the MZ modulator-and modulated light from the MZ modulator-are combined and provided to the second input of the PBRC. The PBRCcombines the modulated light from the MZ modulator-and the MZ modulator-with the modulated light from the MZ modulator-and the MZ modulator-to generate the optical transmit signal.

204 2 204 236 240 244 236 240 244 232 204 3 212 On the other hand, when data is to be transmitted via a single wavelength using coherent modulation, the laser control signals are set to turn on the laser-and to turn off the other lasers. Additionally, the optical network control signals are set to configure the variable couplers,,so that the variable couplers,,cross-couple light between the respective first input to the respective second output, and between the respective second input to the respective first output. As a result, the reconfigurable optical networkdelivers light from the laser-to the optical inputs of all of the MZ modulators.

212 212 Additionally, modulator control signals (not shown) configure the MZ modulatorsfor coherent modulation. For example, the modulator control signals select the operating point of the MZ modulatorsto be a second modulator operating point (different than the first operating point) suitable for coherent modulation.

212 1 212 1 212 2 212 2 212 3 212 3 212 4 212 4 220 220 220 Further, modulation signals applied to the MZ modulator-cause the MZ modulator-to generate a first in-phase (I) signal, and modulation signals applied to the MZ modulator-cause the MZ modulator-to generate a first quadrature (Q) signal. Similarly, modulation signals applied to the MZ modulator-cause the MZ modulator-to generate a second I signal, and modulation signals applied to the MZ modulator-cause the MZ modulator-to generate a second Q signal. Further, the first I signal and the first Q signal are combined and provided to the first input of the PBRC; and the second I signal and the second Q signal are combined and provided to the second input of the PBRC. The PBRCcombines the first I signal and the first Q signal with the second I signal and the second Q signal to generate the optical transmit signal. The optical transmit signal includes: i) the first I signal and the first Q signal in a first polarization direction, and ii) the second I signal and the second Q signal in a second polarization direction.

2 FIG.B 2 FIG.A 200 204 236 240 244 236 240 244 232 204 1 212 1 232 204 2 212 2 232 204 3 212 3 232 204 4 212 4 is a diagram of the optical moduleofconfigured to transmit data via multiple wavelengths using intensity modulation, according to an embodiment. The laser control signals are set to turn on all of the lasers. Additionally, the optical network control signals are set to configure the variable couplers,,so that the variable couplers,,do not provide cross-coupling between the respective first input to the respective second output, and between the respective second input to the respective first output. As a result, the reconfigurable optical networkdelivers light from the laser-to the optical input of the MZ modulator-; the reconfigurable optical networkdelivers light from the laser-to the optical input of the MZ modulator-; the reconfigurable optical networkdelivers light from the laser-to the optical input of the MZ modulator-; and the reconfigurable optical networkdelivers light from the laser-to the optical input of the MZ modulator-.

212 212 Additionally, modulator control signals (not shown) have configured the MZ modulatorsfor intensity modulation. For example, the modulator control signals have selected the operating point of the MZ modulatorsto be the first modulator operating point suitable for intensity modulation.

212 212 212 1 212 2 220 212 3 212 4 220 220 212 1 212 2 212 3 212 4 Additionally, the modulation signals control the MZ modulatorsto modulate respective data onto the respective light received by the MZ modulators. Further, modulated light from the MZ modulator-and modulated light from the MZ modulator-are combined and provided to the first input of the PBRC; and modulated light from the MZ modulator-and modulated light from the MZ modulator-are combined and provided to the second input of the PBRC. The PBRCcombines the modulated light from the MZ modulator-and the MZ modulator-with the modulated light from the MZ modulator-and the MZ modulator-to generate the optical transmit signal.

2 FIG.C 2 FIG.A 200 204 2 204 236 240 244 236 240 244 232 204 3 212 is a diagram of the optical moduleofconfigured to transmit data via a single wavelength (e.g., λ3) using coherent modulation, according to an embodiment. The laser control signals are set to turn on the laser-and to turn off the other lasers. Additionally, the optical network control signals are set to configure the variable couplers,,so that the variable couplers,,cross-couple light between the respective first input to the respective second output, and between the respective second input to the respective first output. As a result, the reconfigurable optical networkdelivers light from the laser-to the optical inputs of all of the MZ modulators.

212 212 Additionally, modulator control signals (not shown) have configured the MZ modulatorsfor coherent modulation. For example, the modulator control signals have selected the operating point of the MZ modulatorsto be the second modulator operating point (different than the first operating point) suitable for coherent modulation.

212 1 212 2 260 212 3 212 4 264 260 220 264 The MZ modulator-and the MZ modulator-act as a first IQ modulatorfor an X polarization direction; and the MZ modulator-and the MZ modulator-act as a second IQ modulatorfor a Y polarization direction. Further, a first IQ modulated signal from the first IQ modulatorare combined by the PBRCwith the second IQ modulated signal from the second IQ modulator. The optical transmit signal includes: i) the first IQ signal in a first polarization direction, and ii) the second IQ signal in a second polarization direction.

3 FIG. 1 FIG. 1 FIG. 1 FIG. 300 100 300 300 100 100 300 is a simplified diagram of an example optical receiverthat is reconfigurable to process amplitude-modulated and coherent-modulated signals, according to an embodiment. In an embodiment, the optical transmitter() and the optical receiverare included in a transceiver that is reconfigurable to generate and process amplitude-modulated and coherent-modulated signals. In other embodiments, the optical receiveris included in a transceiver with a suitable reconfigurable optical transceiver different than the optical transmitterof. Similarly, the optical transmitterofis included in a transceiver with another suitable reconfigurable receiver different than the optical receiver, in other embodiments.

300 304 The optical receivercomprises an optical modulethat is configured to i) receive an optical signal via an optical communication medium (not shown), ii) optically process the optical signal to generate a plurality of processed optical signals, and iii) generate a plurality of electrical signals based on the processed optical signals.

300 308 304 308 304 The optical receiveralso comprises a baseband processorcoupled to the optical module. The baseband processoris configured to i) receive the plurality of electrical signals from the optical module, ii) convert the plurality of electrical signals to digital domain signals, iii) process the digital domain signals to recover receive data from the digital domain signals, and iv) output the receive data (e.g., to a host processor (not shown)).

308 304 304 The baseband processorincludes AFE circuitry (not shown) that is configured to convert the plurality of electrical signals from the optical moduleto the digital domain signals. For example, the AFE includes one or more digital-to-analog converters (DACs) that are configured to convert the electrical signals from the optical moduleto the digital domain signals.

308 The baseband processoralso includes a DSP (not shown) that is configured to perform various processing actions such as one or more of i) filtering (e.g., equalization) of the digital domain signals, ii) recovering information bits from the digital domain signals, iii) performing FEC decoding, etc.

308 312 304 312 308 312 312 312 112 The baseband processoralso comprises a controllerthat is configured to generate one or more control signals for reconfiguring the optical modulefor processing optical receive signals according to different demodulation techniques. In other embodiments, the controlleris external to the baseband processor. The controllercomprises a processor coupled to a memory, and the processor is configured to execute machine-readable instructions in the memory that, when executed by the processor, cause the controllerto generate the one or more control signals, according to an embodiment. Additionally or alternatively, the controllercomprises hardware circuitry (e.g., a hardware state machine) that additionally or alternatively causes the controllerto generate the one or more control signals, in another embodiment.

304 320 324 320 328 328 324 The optical modulecomprises a reconfigurable optical networkthat is optically coupled to optical-to-electrical conversion circuitry. The reconfigurable optical networkis also optically coupled to an optical processor. The optical processoris also optically coupled to the optical-to-electrical conversion circuitry.

320 312 328 324 328 304 312 320 324 328 304 312 320 328 In an embodiment, the reconfigurable optical networkis configured to selectively, based on the one or more control signals from the controller, direct light corresponding to optical receive signal i) to the optical processor, or ii) to the optical-to-electrical conversion circuitryin a manner that bypasses the optical processor. For example, in a first configuration of the optical modulethe one or more control signals from the controllercontrol the reconfigurable optical networkto demultiplex multiple wavelengths of light in the optical receive signal and direct the demultiplexed light to the optical-to-electrical conversion circuitryin a manner that bypasses the optical processor; whereas in a second configuration of the optical modulethe one or more control signals from the controllercontrol the reconfigurable optical networkto split the optical receive signal into i) a first polarized optical signal polarized in a first direction and ii) a second polarized optical signal polarized in a second direction, and direct the first polarized optical signal and the second polarized optical signal to the optical processor.

308 320 324 328 324 308 In operation, when the optical signal includes data multiplexed on multiple wavelengths using intensity modulation, the one or more control signals from the baseband processorcontrol the reconfigurable optical networkto demultiplex multiple wavelengths of light in the optical receive signal and direct the demultiplexed light to the optical-to-electrical conversion circuitryin a manner that bypasses the optical processor. The optical-to-electrical conversion circuitrygenerates a plurality of electrical signals based on the demultiplexed light, and the baseband processorprocesses the electrical signals to recover information bits based on intensity demodulation techniques.

308 320 328 328 324 308 On the other hand, when the optical signal corresponds to a dual-polarized coherent modulation, the one or more control signals from the baseband processorcontrol the reconfigurable optical networkto split the optical receive signal into i) a first polarized optical signal polarized in a first direction and ii) a second polarized optical signal polarized in a second direction, and direct the first polarized optical signal and the second polarized optical signal to the optical processor. The optical processorperforms optical processing on the first polarized optical signal and the second polarized optical signal to generate a plurality of processed optical signals. The optical-to-electrical conversion circuitrygenerates a plurality of electrical signals based on the processed optical signals, and the baseband processorprocesses the electrical signals to recover information bits based on coherent demodulation techniques.

4 FIG.A 3 FIG. 4 FIG.A 3 FIG. 3 FIG. 400 400 304 400 300 300 400 is a simplified block diagram of an example optical modulethat can be reconfigured to process an optical receive signal according to different demodulation techniques, according to an embodiment. The optical moduleis used as the optical moduleof, andis described with reference tofor ease of explanation. In other embodiments, the optical moduleis used in another suitable receiver different than the receiverof. Similarly, the receiveruses a suitable optical module different than the optical module, in some embodiments.

400 404 408 404 412 412 408 The optical modulecomprises a reconfigurable optical networkthat is optically coupled to optical-to-electrical conversion circuitry. The reconfigurable optical networkis also optically coupled to an optical processor. The optical processoris also optically coupled to the optical-to-electrical conversion circuitry.

404 312 412 408 412 404 404 408 412 404 404 412 3 FIG. In an embodiment, the reconfigurable optical networkis configured to selectively, based on a control signals from a (e.g., the controller()), direct light corresponding to optical receive signal i) to the optical processor, or ii) to the optical-to-electrical conversion circuitryin a manner that bypasses the optical processor. For example, in a first configuration of the optical modulethe control signal controls the reconfigurable optical networkto demultiplex multiple wavelengths of light in the optical receive signal and direct the demultiplexed light to the optical-to-electrical conversion circuitryin a manner that bypasses the optical processor; whereas in a second configuration of the optical modulethe control signal controls the reconfigurable optical networkto split the optical receive signal into i) a first polarized optical signal polarized in a first direction and ii) a second polarized optical signal polarized in a second direction, and direct the first polarized optical signal and the second polarized optical signal to the optical processor.

404 420 420 420 420 424 420 408 The reconfigurable optical networkcomprises an optical demultiplexerthat is configured to demultiplex multiple optical signals at respective wavelengths from light received an input of the optical demultiplexer, the multiple optical signals having been multiplexed at a transmitter. The demultiplexed optical signals are output via respective outputs of the optical demultiplexer. One of the outputs of the outputs of the optical demultiplexeris optically coupled to an input of an optical switch, and the remaining outputs of the optical demultiplexerare optically coupled to the optical-to-electrical conversion circuitry.

424 408 424 428 424 420 408 438 One of the outputs of the optical switchis coupled to the optical-to-electrical conversion circuitry, and another output of the optical switchis coupled to an input of a polarity beam splitter (PBS). The optical switchselectively provides the one output of the optical multiplexerto either i) optical-to-electrical conversion circuitry, or ii) the PBS, depending on a state of the control signal.

428 428 428 412 The PBSis configured to split an optical signal received at the input of the PBSinto a first output optical signal and a second output optical signal. The first output optical signal corresponds to light in the input signal that is polarized in a first direction, and the second output signal corresponds to light in the input optical signal that is polarized in a second direction different from the first direction. Outputs of the PBSare coupled to inputs of the optical processor.

412 428 412 412 412 412 The optical processoris configured to generate four pairs of outputs based on optical signals received from the PBS. The optical processorcomprises a plurality of optical couplers (e.g., 3 decibel (3 db) optical couplers) and one or more optical phase shifters. In some embodiments, the optical processorcomprises one or more optical delay lines. In some embodiments, the optical processoris configured to optically mix the optical processoris configured to optically mix a received optical signal with a delayed version of the optical signal.

412 412 308 120 120 120 3 FIG. Generally, the type of optical processordepends on the type of optical modulation to be used and/or an amount of optical demodulation processing to be performed by the optical processorversus an amount of demodulation processing to be performed by a baseband processor (e.g., the baseband processor()). In some embodiments, each optical processorcomprises a coherent intradyne dual polarization (2-Pol) 90-degree hybrid device. In other embodiments, each optical processorcomprises one or more delay line interferometers (DLIs). In some embodiments, each optical processorcomprises one or more Mach-Zehnder interferometers (MZIs).

412 412 428 428 412 428 412 428 P t A t A t+θ P t A t A t+θ P t A t A t+θ P t A t A t+θ I,1 LO if if I,2 LO if if Q,1 LO if if Q,2 LO if if I,1 I,2 Q,1 Q,2 LO if if LO In some embodiments in the optical processorcorresponds to a coherent intradyne dual polarization (2-Pol) 90-degree hybrid device, the coherent intradyne 2-Pol 90-degree hybrid deviceis configured to optically mix the optical signals received from the PBSwith a local optical oscillator (not shown), and to generate four pairs of outputs based on optical signals received from the PBS. For instance, the coherent intradyne 2-Pol 90-degree hybrid deviceis configured to generate a pair of in-phase (I) signals and pair of quadrature (Q) signals based on each output of the PBS. In some embodiments involving M-QAM or DQPSK demodulation, for example, the powers of signals output by the coherent intradyne 2-Pol 90-degree hybrid devicecan be represented as:()=¼|()∥|cos(ω)  (Equation 1)()=−¼|()∥|cos(ω)  (Equation 2)()=¼|()∥|sin(ω)  (Equation 3)()=−¼|()∥|sin(ω)  (Equation 4)where P(t) is the optical power of a first I signal, P(t) is the optical power of a second I signal, P(t) is the optical power of a first Q signal, P(t) is the optical power of a second Q signal, A(t) is the signal electric field from the PBS, A(t) is a local oscillator laser electric field. ωand θis the frequency and phase difference between A and A, respectively.

412 428 428 428 428 412 428 412 428 P t A t A t−T P t A t A t−T P t A t A t−T P t A t A t−T I,1 s I,2 s Q,1 s Q,2 s I,i I,2 Q,1 Q,2 s 2 2 2 2 In some embodiments in which each optical processorcorresponds to one or more DLIs, the outputs of each PBSare coupled to a corresponding set of one or more DLIs. The set of one or more DLIsis configured to generate four pairs of outputs based on optical signals received from the PBS. For instance, the DLIis configured to generate a pair of I signals and pair of Q signals based on each output of the PBS. In an embodiment involving DQPSK demodulation, the powers of signals output by the DLIcan be represented as:()=¼|()+()|  (Equation 5)()=−¼|()−()|  (Equation 6)()=¼|()+()|  (Equation 7)()=−¼|()−()|  (Equation 8)where P(t) is the optical power of a first I signal, P(t) is the optical power of a second I signal, P(t) is the optical power of a first Q signal, P(t) is the optical power of a second Q signal, A(t) is the signal from the PBS, and Tis a symbol delay.

408 440 444 440 444 The optical-to-electrical conversion circuitcomprises multiple instances of a respective photodiode circuitcoupled to a respective transimpedance amplifier (TIA). As will be described further below, each photodiode circuitis configured to convert one or more optical signals into a current signal, and the corresponding TIAis configured to convert the current signal into a voltage signal, according to an embodiment.

408 440 420 412 440 420 412 4 FIG.A The optical-to-electrical conversion circuitis configured to process optical signals that are modulated according to multiple different optical modulation techniques. As can be seen from, each of the photodiode circuitsis optically coupled to both i) a respective output of the optical demultiplexerand ii) respective outputs of the optical processor. As will be described further below, each of the photodiode circuitsincludes a multiple-input photodiode that is configured to receive both i) a respective output of the optical demultiplexerand ii) respective outputs of the optical processor.

400 440 420 400 440 412 As will be described further below, when the optical moduleis in a first configuration, each of the photodiode circuitsreceives a respective intensity modulated signal from the optical demultiplexer; and when the optical moduleis in a second configuration, each of the photodiode circuitsreceives a set of optical signals from the optical processor.

400 440 420 400 440 444 When the optical moduleis in the first configuration, each of the photodiode circuitsis configured to generate a current signal that corresponds to an intensity modulated signal from the optical demultiplexer. When the optical moduleis in the second configuration, each pair of photodiode circuitand TIAis configured to generate a voltage signal that corresponds to a subtraction of either i) a corresponding pair of I signals (e.g., Equations 1 and 2, or Equations 5 and 6), or ii) a corresponding pair of Q signals (e.g., Equations 3 and 4, or Equations 7 and 8), according to an embodiment.

4 FIG.B 400 400 is an illustration of the optical modulein a first configuration in which the optical moduleis configured to receive intensity-modulated signals multiplexed on multiple wavelengths, according to an embodiment.

420 424 440 424 424 440 2 428 428 412 412 440 428 412 400 4 FIG.A 4 FIG.A 4 FIG.B The optical demultiplexerdemultiplexes the optical receive signal input into four outputs. One of the outputs is provided to the optical switch, whereas the three remaining outputs of the demultiplexer are provided to respective photodiode circuits. In the first configuration, the control signal provided to the optical switchcontrols the optical switchto direct the one output of the demultiplexer to photodiode circuit-. As a result, the PBS() does not receive an optical signal. Thus, the PBSdoes not provide any optical signals to the optical processor(), and the optical processordoes not provide any optical signals to the photodiode circuits. Accordingly, the PBSand the optical processorare not illustrated into help show the paths of optical signals through the optical modulewhile in the first configuration.

440 420 444 440 Each of the photodiode circuitsgenerates a respective current signal that corresponds to an intensity-modulated signal from a respective output of the optical demultiplexer. The TIAsgenerate respective voltage signals based on the current signals from the photodiode circuits.

4 FIG.C 4 FIG.C 400 400 412 412 is an illustration of the optical modulein a second configuration in which the optical moduleis configured to receive and demodulate dual-polarity DQPSK signals or M-QAM signals, according to an embodiment. In the embodiment of, the optical processorcorresponds to a coherent intradyne 2-Pol 90-degree hybrid device. The DQPSK-modulated or M-QAM signals are modulated on the λ3 wavelength.

420 420 424 424 424 428 Because the optical receive signal only includes the λ3 wavelength, three outputs of the optical demultiplexerhave no signal, and the output of the optical demultiplexercorresponding to the λ3 wavelength is provided to the optical switch. In the second configuration, the control signal provided to the optical switchcontrols the optical switchto direct the λ3 wavelength output of the demultiplexer to the PBS.

428 412 412 428 The PBSsplits an input optical signal into a first output optical signal (corresponding to light polarized in a first direction) and a second output optical signal (corresponding to light polarized in a second direction), and the coherent intradyne 2-Pol 90-degree hybrid devicereceives the first optical signal and the second optical signal. The coherent intradyne 2-Pol 90-degree hybrid devicegenerates a pair of I signals and a pair of Q signals based on each output of the PBS, as discussed above.

440 440 444 Each photodiode circuitreceives a corresponding pair of I signals (e.g., Equations 1 and 2), or ii) a corresponding pair of Q signals (e.g., Equations 3 and 4), and each photodiode circuit/TIApair generates a voltage signal that corresponds to a subtraction of i) the corresponding pair of I signals, or ii) the corresponding pair of Q signals.

4 FIG.D 1 FIG.D 400 100 412 is an illustration of the optical modulein the second configuration in which the optical receiveris configured to receive and demodulate multiple DQPSK signals, according to another embodiment. In the embodiment of, each optical processorcorresponds to a set of one or more DLIs.

4 FIG.D 4 FIG.C 412 412 424 428 In the embodiment of, more of the demodulation processing is performed in the DLIs(optical processors) and therefore less demodulation processing need be performed by the baseband processor as compared to the embodiment of. In an embodiment, a polarization controller (PC) is coupled between the optical switchand the input of the PBS.

5 FIG.A 3 FIG. 4 FIG.A 4 FIG.A 4 FIG.A 5 FIG.A 500 300 400 500 500 400 400 500 is a simplified diagram of an example optical-to-electrical conversion circuitfor use with reconfigurable optical receivers such as the optical receiverofand reconfigurable optical modules such as the reconfigurable optical moduleof, according to an embodiment. The optical-to-electrical conversion circuitis described with reference tofor ease of explanation. In some embodiments, the optical-to-electrical conversion circuitis used in a suitable reconfigurable optical module different than the reconfigurable optical moduleof. Similarly, the optical moduleuses a suitable optical-to-electrical conversion circuit that is different than the optical-to-electrical conversion circuitof.

500 444 1 444 1 440 2 444 2 440 3 444 3 440 4 444 4 In an embodiment, the optical-to-electrical conversion circuitis used for each of i) the photodiode circuitry-and the TIA-, ii) the photodiode circuitry-and the TIA-, iii) the photodiode circuitry-and the TIA-, and iv) the photodiode circuitry-and the TIA-.

500 504 508 504 512 516 512 520 524 516 528 532 516 512 532 516 520 512 528 The optical-to-electrical conversion circuitcomprises a photodiode circuitcoupled to a TIA. The photodiode circuitcomprises a photodiodeand a multiple-input photodiode. The photodiodecomprises an anodeand a cathode, and the multiple-input photodiodecomprises an anodeand a cathode. The multiple-input photodiodeis coupled in series with the photodiode. For example, the cathodeof the multiple-input photodiodeis coupled to the anodeof the photodiode. In an embodiment, the anodeis coupled to ground.

504 540 512 516 The photodiode circuitalso comprises bias circuitrythat is configured to apply a reverse bias across the photodiodeand the multiple-input photodiode.

508 544 548 544 544 548 544 The TIAcomprises an operational amplifierand an impedancethat is coupled between an input of the operational amplifierand an output of the operational amplifier. In an embodiment, the impedanceis a suitable resistance. In an embodiment, the operational amplifiercomprises an additional input (not shown) coupled to ground.

508 508 In other embodiments, the TIAcomprises other suitable circuitry (e.g., that does not include an operational amplifier and/or does not include an impedance coupled between an input of the operational amplifier and an output of the operational amplifier) configured to convert a current signal to a voltage signal. As merely an illustrative example, the TIAcomprises a common gate/common base amplifier.

504 512 516 532 516 520 512 512 516 In other embodiments, the photodiode circuitcomprises another suitable arrangement of the photodiodeand the multiple-input photodiode. For example, in some embodiments, the cathodeof the multiple-input photodiodeis not coupled to the anodeof the photodiode. In some such embodiments, each of the photodiodeand the multiple-input photodiodeis coupled to respective inputs of another suitable TIA and/or to respective inputs of respective TIAs.

504 560 512 516 544 560 544 520 532 560 544 520 532 The photodiode circuitincludes a nodecoupled between the photodiodeand the multiple input photodiode, and also coupled to the input of the operational amplifier. The nodeoutputs a current to the operational amplifierthat is a sum of i) current flowing from the anodeand ii) current flowing from the cathode. In other words, the nodeoutputs a current to the operational amplifierthat is a difference of i) current flowing from the anodeand ii) current flowing into the cathode.

560 520 532 560 560 512 516 560 512 516 508 In an embodiment, the nodecomprises a connection between the anodeand the cathode. In other embodiments, the nodecomprises one or more passive components (not shown). For example, the nodecomprises a first resistor (not shown) in series with the photodiodeand a second resistor (not shown) in series with the multiple-input photodiode. In other embodiments, the node comprises one or more active components (not shown). For example, the nodecomprises one or more transistors (not shown) arranged to act as an amplifier and/or buffer between i) the photodiodeand the multiple-input photodiode, and ii) the TIA.

512 520 512 516 532 516 560 520 532 508 560 In operation, when an optical signal illuminates the photodiode, a current flowing out of the anodeincreases with the intensity of light illuminating the photodiode. Similarly, when an optical signal illuminates the multiple-input photodiode, a current flowing into the cathodeincreases with the intensity of light illuminating the multiple-input photodiode. Additionally, as discussed above, current output by the nodecorresponds to a difference of i) current flowing from the anodeand ii) current flowing into the cathode. The TIAacts to convert the current signal output by the nodeto a voltage signal.

5 FIG.A 516 516 500 440 1 444 1 516 420 412 In the example of, the multiple-input photodiodeis configured to receive three optical signals. In other embodiments, the multiple-input photodiodeis configured to receive two optical signals. For example, in an embodiment in which the optical-to-electrical conversion circuitis used for the photodiode circuitry-and the TIA-, the multiple-input photodiodereceives a first optical signal from the optical demultiplexerand a second optical signal from the optical processor.

516 516 532 532 500 500 500 500 420 412 420 412 In an embodiment, the multiple-input photodiodecomprises a front side and a back side that is opposite the front side; and the multiple-input photodiodeis configured so that when light illuminates the front side a current flowing into the cathodeincreases with the intensity of light illuminating the front side, and when light illuminates the back side the current flowing into the cathodeincreases with the intensity of light illuminating the back side. In such embodiments, the optical-to-electrical conversion circuit(and/or an optical module that includes the optical-to-electrical conversion circuit) is configured to direct light from a first source to the front side and to direct light from a second source to the back side. For example, the optical-to-electrical conversion circuit(and/or an optical module that includes the optical-to-electrical conversion circuit) is configured to direct to the front side light from one of the optical demultiplexerand the optical processor, and to direct to the back side light from another one of the optical demultiplexerand the optical processor.

516 516 420 412 516 512 516 512 In another embodiment, the multiple-input photodiodeadditionally or alternatively comprises an active region on one side of the multiple-input photodiodehaving a size configured to accommodate receiving optical signals from multiple sources. For example, the size of the active region is configured to accommodate receiving optical signals from at least the optical demultiplexerand the optical processor. In an embodiment, the size of the active region of the multiple-input photodiodeis substantially larger (i.e., at least 20% larger) than a size of an active region of the photodiode. In other embodiments, the size of the active region of the multiple-input photodiodeis not substantially larger than the size of the active region of the photodiode.

4 5 FIGS.A andA 412 512 412 516 412 512 412 512 512 412 Referring now to, in an embodiment, the optical processoris optically coupled to the photodiodevia a waveguide that guides light from an output of the optical processorto the multiple-input photodiode. In another embodiment, the optical processoris optically coupled to the photodiodevia a fiber optic cable that guides light from an output of the optical processorto the photodiode. In another embodiment, the photodiodereceives light from an output of the optical processorvia free space.

420 516 420 516 412 516 412 516 420 516 516 412 516 516 516 In an embodiment, the optical demultiplexeris optically coupled to the multiple-input photodiodevia a first waveguide that guides light from an output of the optical demultiplexerto the multiple-input photodiode; and an output of the optical processoris optically coupled to the multiple-input photodiodevia a second waveguide that guides light from an output of the optical processorto the multiple-input photodiode. In some such embodiments, the first waveguide guides light from the output of the optical demultiplexerto one of the front side of the multiple-input photodiodeand the back side of the multiple-input photodiode; and the second waveguide guides light from the output of the optical processorto another one of the front side of the multiple-input photodiodeand the back side of the multiple-input photodiode. In other such embodiments, the active region on one side of the multiple-input photodiodehas a size configured to accommodate receiving light from the first waveguide and receiving light from the second waveguide.

420 516 420 516 412 516 412 516 420 516 516 412 516 516 516 In another embodiment, the optical demultiplexeris optically coupled to the multiple-input photodiodevia a first fiber optic cable that guides light from an output of the optical demultiplexerto the multiple-input photodiode; and the optical processoris optically coupled to the multiple-input photodiodevia a second fiber optic cable that guides light from an output of the optical processorto the multiple-input photodiode. In some such embodiments, the first fiber optic cable guides light from the output of the optical demultiplexerto one of the front side of the multiple-input photodiodeand the back side of the multiple-input photodiode; and the second fiber optic cable guides light from the output of the optical processorto another one of the front side of the multiple-input photodiodeand the back side of the multiple-input photodiode. In other such embodiments, the active region on one side of the multiple-input photodiodehas a size configured to accommodate receiving light from the first fiber optic cable and receiving light from the second fiber optic cable.

516 420 412 500 304 400 420 516 516 412 516 516 516 420 412 In another embodiment, the multiple-input photodiodereceives light from an output of the optical demultiplexervia free space, and receives light from an output of the optical processorvia free space. In some such embodiments, optical-to-electrical conversion circuitryand/or the optical module (e.g., the optical module, the optical module, etc.) is configured: i) to direct light via free space from the output of the optical demultiplexerto one of the front side of the multiple-input photodiodeand the back side of the multiple-input photodiode; and ii) direct light via free space from the output of the optical processorto another one of the front side of the multiple-input photodiodeand the back side of the multiple-input photodiode. In other such embodiments, the active region on one side of the multiple-input photodiodehas a size configured to accommodate receiving light from the optical demultiplexervia free space and receiving light from the output of the optical processorvia free space.

516 420 412 420 516 516 412 516 516 516 420 412 In other embodiments, the multiple-input photodiodereceives light from an output of the optical demultiplexervia one of a waveguide, a fiber optic cable, free space, etc., and receives light from an output of the optical processorvia another one of a waveguide, a fiber optic cable, free space, etc. In some such embodiments, light from the optical demultiplexeris directed to one of the front side of the multiple-input photodiodeor the back side of the multiple-input photodiode, and light from the optical processoris directed to another one of the front side of the multiple-input photodiodeor the back side of the multiple-input photodiode. In some other such embodiments, the active region on one side of the multiple-input photodiodehas a size configured to accommodate receiving light from the optical demultiplexervia the one of a waveguide, a fiber optic cable, free space, etc., and receiving light from the output of the optical processorvia the other one of a waveguide, a fiber optic cable, free space, etc.

516 300 516 516 The different optical signals that the multiple-input photodiodeis configured to receive correspond to different modulation techniques. For example, in the optical receiver, the one of the optical signals that the multiple-input photodiodeis configured to receive corresponds to an intensity-modulated optical signal, and another one of the optical signals that the multiple-input photodiodeis configured to receive corresponds to a coherent-modulated signal.

5 FIG.B 5 FIG.A 3 4 4 FIGS.,A, andB 500 300 500 440 1 444 1 516 412 516 420 512 412 560 420 508 is a diagram of the optical-to-electrical conversion circuitofoperating when the optical receiveris operating in the first configuration, such as described above with reference to, according to an embodiment. For example, when the optical-to-electrical conversion circuitis used as the photodiode circuit-and the TIA-, the multiple-input photodiodedoes not receive an optical signal from the optical processor. Rather, the multiple-input photodiodereceives an optical signal (e.g., an IMDD signal) from the optical demultiplexer. Additionally, the photodiodedoes not receive an optical signal from the optical processor. Thus, the current signal output from the nodereflects variations in the intensity of light in the IMDD signal from the optical demultiplexer. The TIAconverts this current signal to a voltage signal.

5 FIG.C 5 FIG.A 3 4 4 4 FIGS.,A,C, andD 4 FIG.C 500 300 500 440 1 444 1 512 412 516 420 516 412 560 520 532 is a diagram of the optical-to-electrical conversion circuitofoperating when the optical receiveris operating in the second configuration, such as described above with reference to, according to an embodiment. For example, when the optical-to-electrical conversion circuitis used as the photodiode circuit-and the TIA-of, the photodiodereceives a first optical signal (e.g., a first DQSPK signal) from the optical processor, such as an optical signal corresponding to Equation 1. Additionally, the multiple-input photodiodedoes not receive an optical signal from the optical demultiplexer. Rather, the multiple-input photodiodereceives a second optical signal (e.g., a second DQSPK signal) from the optical processor, such as an optical signal corresponding to Equation 2. Thus, the current signal output from the nodecorresponds to a difference of i) current flowing from the anodedue to the first optical signal and ii) current flowing into the cathodedue to the second optical signal.

560 P t P t |A t A t+θ I,1 I,2 LO if if When the first optical signal corresponds to Equation 1 and the second optical signal corresponds to Equation 2, the current signal output from the nodeis proportional to:()−()=½()∥|cos(ω)  (Equation 9)

444 560 The TIAconverts the current signal output by the nodeto a voltage signal.

500 440 1 444 1 512 412 516 420 516 412 560 520 532 4 FIG.D As another example, when the optical-to-electrical conversion circuitis used as the photodiode circuit-and the TIA-of, the photodiodereceives a first optical signal (e.g., a first DQSPK signal) from the set of DLIs, such as an optical signal corresponding to Equation 5. Additionally, the multiple-input photodiodedoes not receive an optical signal from the optical demultiplexer. Rather, the multiple-input photodiodereceives a second optical signal (e.g., a second DQSPK signal) from the set of DLIs, such as an optical signal corresponding to Equation 6. Thus, the current signal output from the nodecorresponds to a difference of i) current flowing from the anodedue to the first optical signal and ii) current flowing into the cathodedue to the second optical signal.

560 560 P t P t A t A t−T A t P i t P t P t I,1 I,2 s 0 0 I,1 I,2 When the first optical signal corresponds to Equation 5 and the second optical signal corresponds to Equation 6, the current signal output from the nodeis proportional to:()−()=()()  (Equation 10)where A(t) equals:()=sqrt()exp[φ()]  (Equation 11)Where Pis a constant and φ(t) is the phase of the optical signal. Then, the current signal output from the nodeis proportional to:()−()=cos(Δφ)  (Equation 12)where Δφ(t)=φ(t)−φ(t−Ts), and is 0 or π depending on the bit transmitted.

444 560 308 444 The TIAconverts the current signal output by the nodeto a voltage signal. In DQPSK, Δφ=0 or π depending on the bit transmitted, and the DSP of the baseband processorcan reconstruct the original bit stream from the output of the TIA.

5 FIG.D 5 FIG.A 3 4 FIGS.andA 500 100 412 412 428 500 440 1 444 1 512 412 516 420 516 412 560 520 532 is a diagram of the optical-to-electrical conversion circuitofoperating when the optical receiveris operating in the configuration corresponding to intradyne M-QAM demodulation, according to an embodiment. Referring again to, with intradyne M-QAM demodulation, the optical processorcomprises a coherent intradyne 2-pol 90-degree hybrid, which mixes optical signals from the PBSwith a local oscillator signal (not shown) as part of generating the output signals. When the optical-to-electrical conversion circuitis used as the photodiode circuit-and the TIA-, the photodiodereceives a first optical signal (e.g., a first intradyne M-QAM signal) from the coherent intradyne 2-pol 90-degree hybrid, such as an optical signal corresponding to Equation 1. Additionally, the multiple-input photodiodedoes not receive an optical signal from the optical demultiplexer. Rather, the multiple-input photodiodereceives a second optical signal (e.g., a second intradyne M-QAM signal) from the coherent intradyne 2-pol 90-degree hybrid, such as an optical signal corresponding to Equation 2. Thus, the current signal output from the nodecorresponds to a difference of i) current flowing from the anodedue to the first optical signal and ii) current flowing into the cathodedue to the second optical signal.

560 508 560 When the first optical signal corresponds to Equation 1 and the second optical signal corresponds to Equation 2, the current signal output from the nodeis proportional to Equation 9. The TIAconverts the current signal output by the nodeto a voltage signal.

6 FIG. 1 FIG. 2 FIG.A 6 FIG. 1 2 FIGS.andA 1 FIG. 2 FIG.A 600 600 200 600 200 is a flow diagram of an example methodfor operating a reconfigurable optical transmitter that is capable of modulating optical signals according to different optical modulation techniques, according to an embodiment. The methodis implemented by the reconfigurable optical transmitter ofand/or using the optical moduleof, in some embodiments.is described with reference tofor explanatory purposes. In other embodiments, the methodis implemented using another suitable reconfigurable optical receiver different than the reconfigurable optical receiver ofand/or using another suitable optical module different than the optical moduleof.

604 At block, a type of modulation that the reconfigurable optical transmitter is to use is determined. The reconfigurable optical transmitter is capable of modulating optical signals according to a plurality of different types of optical modulation techniques, including at least a first type and a second type. In an embodiment, the first type corresponds to intensity-modulation in which a plurality of signals are modulated on different wavelengths, and the second type involves coherent modulation on a single wavelength, in an embodiment. For example, the first type corresponds to IMDD modulation, and the second type corresponds to DQPSK or M-QAM, in an illustrative embodiment.

100 704 112 100 604 In an embodiment, the controller of the optical receiverdetermines the type of modulation at block. In another embodiment, the controllerof the optical transmitterdetermines the type of modulation at block.

604 608 608 112 120 204 120 204 In response to determining at blockthat the reconfigurable optical transmitter is to use the first type of modulation, the flow proceeds to block. At block, a controller of the optical transmitter controls multiple lasers of the optical transmitter so that the multiple lasers are turned on. In an embodiment, the multiple lasers correspond to respective wavelengths. For example, the controllercontrols the lasers/so that all of the lasers/are turned on.

610 112 212 At block, the controller configures optical modulators of the optical transmitter for the first type of modulation. For example, the controllersets a modulator operating point of the MZ modulatorsto a first modulator operating suitable for the first type of modulation.

612 112 124 232 120 204 128 212 At block, the controller of the optical transmitter controls a reconfigurable optical network of the optical transmitter so that light from the multiple lasers are provided to respective modulators of the optical transmitter. For example, the controllercontrols the reconfigurable optical network/so that light from the multiple lasers/are provided to respective modulators/of the optical transmitter.

616 104 128 212 616 132 104 132 104 At block, the multiple modulators modulate respective data onto multiple wavelengths according to the first type of modulation. In an embodiment, the baseband processorgenerates modulation signals, which are used to control the multiple modulators/to modulate respective data onto multiple wavelengths according to the first type of modulation. In an embodiment, modulating respective data onto multiple wavelengths at blockcomprises receiving at driver circuitrymodulation signals from the baseband processorand controlling the multiple modulators with the driver circuitrybased on the modulation signals from the baseband processor.

604 620 620 112 120 204 120 204 204 2 120 204 204 1 204 3 204 4 On the other hand, in response to determining at blockthat the reconfigurable optical transmitter is to use the second type of modulation, the flow proceeds to block. At block, the controller of the optical transmitter controls the multiple lasers of the optical transmitter so that one laser is turned on and other lasers are turned off. In an embodiment in which the multiple lasers correspond to respective wavelengths, the controller of the optical transmitter controls the multiple lasers of the optical transmitter so that one laser at one wavelength is turned on and other lasers at other respective wavelengths are turned off. For example, the controllercontrols the lasers/so that one of the lasers/(e.g., laser-) is turned on and the remaining lasers/(e.g., the lasers-,-, and-) are turned off.

622 112 212 At block, the controller configures the optical modulators of the optical transmitter for the second type of modulation. For example, the controllersets the modulator operating point of the MZ modulatorsto a second modulator operating point (different than the first modulator operating point) suitable for the second type of modulation.

624 112 124 232 120 204 204 2 128 212 At block, the controller of the optical transmitter controls the reconfigurable optical network of the optical transmitter so that light from the one laser is provided to multiple modulators of the optical transmitter. For example, the controllercontrols the reconfigurable optical network/so that light from the one laser/(e.g., laser-) is provided to all of the modulators/of the optical transmitter.

628 104 128 212 628 132 104 132 104 At block, the multiple modulators modulate respective data onto one wavelength according to the second type of modulation. In an embodiment, the baseband processorgenerates modulation signals, which are used to control the multiple modulators/to modulate data onto one wavelength according to the first type of modulation. In an embodiment, modulating data onto one wavelength at blockcomprises receiving at driver circuitrymodulation signals from the baseband processorand controlling the multiple modulators with the driver circuitrybased on the modulation signals from the baseband processor.

7 FIG. 3 FIG. 4 FIG.A 7 FIG. 3 4 FIGS.andA 3 FIG. 4 FIG.A 700 700 400 700 is a flow diagram of an example methodfor operating a reconfigurable optical receiver that is capable of demodulating optical signals that are modulated according to different optical modulation techniques, according to an embodiment. The methodis implemented using the reconfigurable optical receiver ofand/or the reconfigurable optical moduleof, in an embodiment.is described with reference tofor explanatory purposes. In other embodiments, the methodis implemented using another suitable reconfigurable optical receiver different than the reconfigurable optical receiver ofand/or using another suitable reconfigurable optical module different than the reconfigurable optical module of.

704 At block, a type of modulation that the reconfigurable optical receiver is to process is determined. The reconfigurable optical receiver is capable of demodulating optical signals that are modulated according to a plurality of different types of optical modulation techniques, including at least a first type and a second type. In an embodiment, the first type does not involve use of an optical processor of the reconfigurable optical receiver, and the second type involves use of an optical processor. For example, the first type corresponds to intensity modulation (e.g., IMDD modulation), and the second type corresponds to coherent modulation (e.g., DQPSK or M-QAM modulation), in an embodiment.

312 300 704 In an embodiment, the controllerof the optical receiverdetermines the type of modulation at block.

704 708 708 328 404 420 412 312 300 424 420 412 420 In response to determining at blockthat the type of modulation that the reconfigurable optical receiver is to process is the first type, the flow proceeds to block. At block, a reconfigurable optical network of the reconfigurable optical receiver is controlled so that an optical signal corresponding to a signal received by the reconfigurable optical receiver bypasses an optical processor of the reconfigurable optical receiver. For example, the reconfigurable optical network/is controlled so that an output of the optical demultiplexerbypasses the optical processor. For example, the controllerof the optical receivergenerates a control signal to control the optical switchso that the output of the optical demultiplexerbypasses the optical processor. In another embodiment in which the reconfigurable optical network includes an optical switch coupled to an input of the optical demultiplexer, a control signal controls the optical switch so that an optical signal bypasses the optical processor and is provided to an input of the optical demultiplexer.

712 708 420 412 440 2 At block, the optical signal that bypasses the optical signal at blockis provided to a multiple-input photodiode of a photodiode circuit of the reconfigurable optical receiver. For example, the output of the optical demultiplexerbypasses the optical processorand is received at a first side of a multiple-input photodiode of the photodiode circuit-.

704 716 716 328 404 420 428 412 312 300 424 420 428 420 428 On the other hand, in response to determining at blockthat the type of modulation that the reconfigurable optical receiver is to process is the second type, the flow proceeds to block. At block, the reconfigurable optical network of the reconfigurable optical receiver is controlled so that the optical signal corresponding to the signal received by the reconfigurable optical receiver is provided to the optical processor of the reconfigurable optical receiver. For example, the reconfigurable optical network/is controlled so that an output of the optical demultiplexeris provided to the PBS, which is coupled to the optical processor. For example, the controllerof the optical receivergenerates a control signal to control the optical switchso that the output of the optical demultiplexeris provided to the PBS. In another embodiment in which the reconfigurable optical network includes an optical switch coupled to an input of the optical demultiplexer, a control signal controls the optical switch so that an optical signal bypasses the optical demultiplexerand is provided to an input of the PBS.

720 120 412 440 412 124 412 At block, multiple outputs of the optical processor are provided to the photodiode circuit of the reconfigurable optical receiver, including providing a first output of the optical processorto the multiple-input photodiode. For example, outputs of the optical processorare provided to the photodiode circuits, including providing a first output of the optical processorto a second side of the multiple-input photodiode of the photodiode circuit, the second side being opposite to the first side of the multiple-input photodiode. In another embodiment, the first output of the optical processorto an active region on the first side of the multiple-input photodiode.

724 124 1 128 1 At block, a current signal output of the photodiode circuit is converted to a voltage signal using a TIA. For example, a current signal output by the photodiode circuit-is converted to a voltage signal by the TIA-.

728 724 308 128 1 At block, the voltage signal generated at blockis sampled by an ADC to generate a digital domain signal. For example, an ADC of the baseband processorsamples the voltage signal output by the TIA-.

732 732 308 Embodiment 1: An optical module for use with multiple optical modulation techniques, the optical, the optical module comprising: a plurality of lasers, each of at least some of the lasers configured to be selectively turned on and turned off depending on a type of modulation to be used, each laser corresponding to a respective wavelength; an optical modulation system comprising a plurality of optical modulators; and a reconfigurable optical network that is configured to selectively direct light from the plurality of lasers to the optical modulation system differently depending on the type of modulation to be used. Embodiment 2: The optical module of embodiment 1, wherein: the plurality of lasers are configurable so that multiple lasers among the plurality of lasers are i) turned on in a first configuration of the optical module and ii) turned off in a second configuration of the optical module; and the reconfigurable optical network is configurable so that i) light from respective lasers among the multiple lasers are directed to respective modulators in the first configuration, and ii) light from a first laser that is turned on in the second configuration is directed to multiple modulators in the second configuration. Embodiment 3: The optical module of embodiment 2, wherein the reconfigurable optical network comprises: a first variable optical coupler having i) a first input coupled to the first laser, ii) a first output, and iii) a second output; a second variable optical coupler having i) a first input coupled to the first output of the first variable optical coupler, ii) a first output coupled to an input of a first optical modulator among the plurality of optical modulators, and iii) a second output coupled to an input of a second optical modulator among the plurality of optical modulators; and a third variable optical coupler having i) a first input coupled to the second output of the first variable optical coupler, ii) a first output coupled to an input of a third optical modulator among the plurality of optical modulators, and iii) a second output coupled to an input of a fourth optical modulator among the plurality of optical modulators. Embodiment 4: The optical module of embodiment 3, wherein: the first variable optical coupler includes a second input coupled to a second laser among the plurality of lasers; the second variable optical coupler includes a second input coupled to a third laser among the plurality of lasers; and a third variable optical coupler includes a second input coupled to a fourth laser among the plurality of lasers. Embodiment 5: An optical transceiver comprising the optical module of any of embodiments 1-4, the optical transceiver further comprising: a controller configured to generate control signals to selectively turn on and turn off the at least some of the lasers depending on the type of modulation to be used; and a baseband processor configured to receive data that is to be transmitted, and generate, based on the data that is to be transmitted, modulation signals for controlling the plurality of optical modulators. Embodiment 6: The optical transceiver of embodiment 5, wherein baseband processor includes the controller. Embodiment 7: A method of controlling a reconfigurable optical module for transmitting information via an optical medium, the method comprising: determining, at a controller, a type of modulation that is to be used to transmit the information via the optical medium, the type of modulation being determined from a plurality of different types of optical modulation techniques, including at least a first type and a second type; controlling, by the controller, a plurality of lasers of the reconfigurable optical module to one of i) turn on or ii) turn off at least some of lasers among the plurality of lasers depending on the type of modulation to be used, each laser corresponding to a respective wavelength; and controlling, by the controller, a reconfigurable optical network of the reconfigurable optical module to selectively direct light from the plurality of lasers to an optical modulation system of the reconfigurable optical module differently depending on the type of modulation to be used. Embodiment 8: The method of controlling the reconfigurable optical module of embodiment 7, wherein: controlling the plurality of lasers comprises controlling the plurality of lasers so that multiple lasers among the plurality of lasers are i) turned on in the first configuration of the optical module, and ii) turned off in the second configuration of the optical module; and controlling the reconfigurable optical network comprises controlling the reconfigurable optical network so that i) light from respective lasers among the multiple lasers are directed to respective modulators in the first configuration, and ii) light from a first laser that is turned on in the second configuration is directed to multiple modulators in the second configuration. Embodiment 9: The method of controlling the reconfigurable optical module of either of embodiments 7 or 8, wherein controlling the reconfigurable optical network comprises: controlling a first variable optical coupler having a first input coupled to the first laser, so that light from the first laser i) is directed only to a first output of the first variable optical coupler in the first configuration, and iii) is directed to the first output of the first variable optical coupler and a second output of the first variable optical coupler in the second configuration; controlling a second variable optical coupler having a first input coupled to the first output of the first variable optical coupler so that light from the first laser i) is directed, in the first configuration, only to a first output of the second variable optical coupler that is coupled to a first modulator among the plurality of modulators, and iii) is directed, in the second configuration, to the first output of the first variable optical coupler and a second output of the second variable optical coupler that is coupled to a second modulator among the plurality of modulators; and controlling a third variable optical coupler having a first input coupled to the second output of the first variable optical coupler so that light received via the first input of the third variable optical coupler i) is directed, in the first configuration, only to a first output of the third variable optical coupler that is coupled to a third modulator among the plurality of modulators, and iii) is directed, in the second configuration, to the first output of the first variable optical coupler and a second output of the second variable optical coupler that is coupled to a fourth modulator among the plurality of modulators. Embodiment 10: The method of controlling the reconfigurable optical module of embodiment 9, controlling the reconfigurable optical network further comprises: controlling the first variable optical coupler so that light from a second laser coupled to a second input of the first variable optical coupler is directed only to the second output of the first variable optical coupler in the first configuration; controlling the second variable optical coupler so that light from a third laser coupled to a second input of the second variable optical coupler is directed, in the first configuration, only to the second output of the second variable optical coupler; and controlling the third variable optical coupler so that light from a fourth laser coupled to a second input of the third variable optical coupler is directed, in the first configuration, only to the second output of the third variable optical coupler. Embodiment 11: A method of controlling an optical transceiver comprising the method of any of embodiments 7-10, the method of controlling the optical transceiver further comprising: receiving, at a baseband processor of the transceiver, data that is to be transmitted via an optical medium; generating, at the baseband processor, modulation signals for controlling the plurality of optical modulators based on the data received at the baseband processor; and providing the modulation signals to the optical module to control the plurality of optical modulators. Embodiment 12: An optical module for use with multiple optical modulation techniques, the optical module comprising: optical-to-electrical conversion circuitry that includes a plurality of photodiodes coupled to a plurality of transimpedance amplifiers (TIAs), the plurality of photodiodes including multiple-input photodiodes, each multiple-input photodiode including a first side and a second side that is opposite the first side; an optical processor that is configured to optically process one or more optical signals corresponding to coherent modulation, the optical processor being coupled to the plurality of photodiodes, including multiple outputs of the optical processor coupled to the respective first sides of the multiple-input photodiodes; and an optical network that is configured to i) in a first configuration corresponding to a first modulation technique, direct optical signals corresponding to light received via an optical medium to the respective second sides of the multiple-input photodiodes so that the light bypasses the optical processor, and ii) in a second configuration corresponding to a second modulation technique, direct one or more optical signals corresponding to light received via the optical medium to one or more inputs of the optical processor. Embodiment 13: The optical module of embodiment 12, wherein the optical network comprises: an optical demultiplexer having a plurality of outputs optically coupled to the respective second sides of the multiple-input photodiodes. Embodiment 14: The optical module of embodiment 13, wherein the optical network further comprises: an optical switch having i) an input coupled to one of the outputs of the optical demultiplexer, ii) a first output coupled to a second side of one of the multiple-input photodiodes, and iii) a second output coupled to one or more inputs of the optical processor, wherein i) in the first configuration corresponding to the first modulation technique, the optical switch directs an optical signal from the one output of the optical demultiplexer to the second sides of the one multiple-input photodiode, and ii) in the second configuration corresponding to the second modulation technique the optical switch directs the optical signal from the one output of the optical demultiplexer to the one or more inputs of the optical processor. Embodiment 15: The optical module of embodiment 14, wherein the optical network further comprises: a polarization beam splitter coupled between the second output of the optical switch and the optical processor. Embodiment 16: An optical receiver that includes the optical module of any of embodiments 12-15, further comprising: a plurality of analog-to-digital converters (ADCs) coupled to the plurality of TIAs, the plurality of ADCs to convert analog outputs of the TIAs to respective digital domain signals. Embodiment 17: The optical receiver of embodiment 16, further comprising: a baseband processor coupled to the plurality of ADCs, the baseband processor configured to recover information bits from the digital domain signals. Embodiment 18: A method of operating a reconfigurable optical module, the optical module including optical-to-electrical conversion circuitry that includes a plurality of photodiodes coupled to a plurality of transimpedance amplifiers (TIAs), the plurality of photodiodes including multiple-input photodiodes, each multiple-input photodiode including a first side and a second side that is opposite the first side, the optical module further including an optical processor that is configured to optically process one or more optical signals corresponding to coherent modulation, the optical processor being coupled to the plurality of photodiodes, including multiple outputs of the optical processor coupled to the respective first sides of the multiple-input photodiodes, the method comprising: determining, at a controller, a type of modulation for which the reconfigurable optical module is to process optical signals received via an optical medium, the type of modulation being determined from a plurality of different types of optical modulation techniques, including at least a first type and a second type; and controlling, by a controller, a reconfigurable optical network of the reconfigurable optical module to selectively i) in a first configuration corresponding to a first modulation technique, direct optical signals corresponding to light received via the optical medium to respective first sides of the multiple-input photodiodes so that the light bypasses the optical processor, and ii) in a second configuration corresponding to a second modulation technique, direct one or more optical signals corresponding to light received via the optical medium to one or more inputs of the optical processor. Embodiment 19: The method of operating the reconfigurable optical module of embodiment 18, further comprising, in the first configuration: demultiplexing, with an optical demultiplexer, light at respective wavelengths from an optical signal corresponding to light received via the optical medium; and providing respective optical signals output by the optical demultiplexer the respective second sides of the multiple-input photodiodes. Embodiment 20: The method of operating the reconfigurable optical module of embodiment 19, wherein the reconfigurable optical network includes an optical switch having i) an input coupled to one of the outputs of the optical demultiplexer, ii) a first output coupled to a second side of one of the multiple-input photodiodes, and iii) a second output coupled to one or more inputs of the optical processor, and wherein controlling the reconfigurable optical network comprises: controlling, by the controller, the optical switch so that i) in the first configuration corresponding to the first modulation technique, the optical switch directs an optical signal from the one output of the optical demultiplexer to the second sides of the one multiple-input photodiode, and ii) in the second configuration corresponding to the second modulation technique the optical switch directs the optical signal from the one output of the optical demultiplexer to the one or more inputs of the optical processor. Embodiment 21: The method of operating the reconfigurable optical module of embodiment 20, further comprises, the second configuration: splitting, by a polarization beam splitter, an output signal from the second output of the optical switch into a first polarized signal and a second polarized signal; and providing the first polarized signal and the second polarized signal to inputs of the optical processor. Embodiment 22: A method of operating an optical receiver including the method of any of embodiments 18-21, the method further comprising: converting, by a plurality of analog-to-digital converters (ADCs), analog outputs of the TIAs to respective digital domain signals. Embodiment 23: The method of operating the optical receiver of embodiment 22, further comprising: recovering, by a baseband processor, information bits from the digital domain signals. Embodiment 24: The optical module of any of embodiments 1-6, wherein: the optical modulation system is configurable so that the plurality of modulators are i) configured to modulate according to a first modulation technique when the optical modulation system is in a first configuration, and ii) configured to modulate according to a second modulation technique when the optical modulation system is in a second configuration. Embodiment 25: The method of controlling the reconfigurable optical module of any of embodiments 7-11, further comprising: configuring the optical modulation system so that a plurality of modulators of the optical modulation system are i) configured to modulate according to the first modulation technique when the optical modulation system is in a first configuration, and ii) configured to modulate according to the second modulation technique when the optical modulation system is in a second configuration. Embodiment 24: An optical transceiver comprising i) any of embodiments 1-6 or 24, and ii) any of embodiments 12-17. Embodiment 25: A method of operating an optical transceiver comprising i) any of embodiments 7-11 or 25, and ii) any of embodiments 18-23. At block, a DSP processes the digital domain signal generated at blockto recover information bits from the digital domain signal. For example, the baseband processorprocesses the digital domain signal generated by the ADC.

Some of the various blocks, operations, and techniques described above may be implemented utilizing hardware, a processor executing firmware instructions, a processor executing software instructions, or any suitable combination thereof. When implemented utilizing a processor executing software or firmware instructions, the software or firmware instructions may be stored in any suitable computer readable memory. The software or firmware instructions may include machine readable instructions that, when executed by one or more processors, cause the one or more processors to perform various acts.

When implemented in hardware, the hardware may comprise one or more of discrete components, an integrated circuit, an application-specific integrated circuit (ASIC), a programmable logic device (PLD), etc.

While the present invention has been described with reference to specific examples, which are intended to be illustrative only and not to be limiting of the invention, changes, additions and/or deletions may be made to the disclosed embodiments without departing from the scope of the invention.